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What is the primary difference between double-stranded DNA (dsDNA) and single-stranded DNA (ssDNA) viruses?
What is the primary difference between double-stranded DNA (dsDNA) and single-stranded DNA (ssDNA) viruses?
dsDNA viruses possess two complementary DNA strands, while ssDNA viruses contain only one strand of DNA.
In which part of the host cell do double-stranded DNA (dsDNA) viruses typically replicate?
In which part of the host cell do double-stranded DNA (dsDNA) viruses typically replicate?
The host's nucleus
What is the primary function of the viral RNA-dependent RNA polymerase enzyme in negative-sense ssRNA viruses?
What is the primary function of the viral RNA-dependent RNA polymerase enzyme in negative-sense ssRNA viruses?
To transcribe the negative-sense RNA into a complementary positive-sense RNA before translation into proteins.
What is the characteristic of positive-sense ssRNA viruses that allows them to directly serve as a template for protein synthesis?
What is the characteristic of positive-sense ssRNA viruses that allows them to directly serve as a template for protein synthesis?
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In which part of the host cell do double-stranded RNA (dsRNA) viruses primarily replicate?
In which part of the host cell do double-stranded RNA (dsRNA) viruses primarily replicate?
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What is the function of the helical arrangement of capsomers in viruses?
What is the function of the helical arrangement of capsomers in viruses?
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What is the characteristic shape of icosahedral viruses?
What is the characteristic shape of icosahedral viruses?
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What is the function of the tail fibres in bacteriophages?
What is the function of the tail fibres in bacteriophages?
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What is the main difference between enveloped and non-enveloped viruses?
What is the main difference between enveloped and non-enveloped viruses?
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What is the vulnerability of enveloped viruses?
What is the vulnerability of enveloped viruses?
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Study Notes
Genetic Material in Viruses
- Viruses use genetic material to encode their functions, ensuring continuity and evolution.
- DNA viruses have Deoxyribonucleic Acid (DNA) as their genetic blueprint.
- There are two types of DNA viruses: double-stranded DNA (dsDNA) and single-stranded DNA (ssDNA).
Double-stranded DNA (dsDNA) Viruses
- Possess two complementary DNA strands, wound together in the familiar double helix.
- Examples: Herpesviruses, causing cold sores and genital herpes; Adenoviruses, responsible for a range of illnesses.
- Replicate in the host's nucleus where the cellular DNA is also located.
Single-stranded DNA (ssDNA) Viruses
- Containing just one strand of DNA, these viruses are relatively less common.
- Example: Parvovirus B19, which can cause a mild rash illness called fifth disease.
- Require a host cell to form a complementary strand, which then serves as a template for replication.
RNA Viruses
- Have Ribonucleic Acid (RNA) as their genetic material.
- There are three types of RNA viruses: double-stranded RNA (dsRNA), single-stranded RNA (ssRNA), and satellite RNA.
Double-stranded RNA (dsRNA) Viruses
- Contain complementary RNA strands, but are rarer among RNA viruses.
- Example: Rotavirus, a significant cause of diarrheal disease in infants and young children.
- Replicate primarily in the cytoplasm of the host cell.
Single-stranded RNA (ssRNA) Viruses
- Can be further categorized based on the polarity of RNA.
- There are two types of ssRNA viruses: positive-sense ssRNA (+ssRNA) and negative-sense ssRNA (-ssRNA).
Positive-sense ssRNA (+ssRNA) Viruses
- Their RNA can directly serve as a template for protein synthesis.
- Example: Coronaviruses, including the infamous SARS-CoV-2.
Negative-sense ssRNA (-ssRNA) Viruses
- Their RNA must first be transcribed into a complementary positive-sense RNA by the viral RNA-dependent RNA polymerase enzyme.
- Examples: Influenza virus, which causes seasonal flu; Rabies virus, resulting in a deadly neurological disease.
Structural Diversity
- The structural components of viruses are crucial for protection, host recognition, and entry.
- The capsid, composed of protein subunits known as capsomers, envelopes the virus's genetic material.
Capsid Composition
- There are three types of capsids: helical, icosahedral, and complex.
Helical Capsids
- Resembling rods or threads, these capsids are cylindrical.
- Examples: Tobacco Mosaic Virus, which affects tobacco plants; Rabies virus.
- Function: The helical arrangement provides a protective shield for the nucleic acid.
Icosahedral Capsids
- Resembling 20-sided dice, these capsids are nearly spherical but polygonal.
- Examples: Polioviruses; Adenoviruses.
- Function: This compact shape offers a stable environment for the viral genetic material.
Complex Capsids
- These capsids exhibit both helical and icosahedral properties or might have additional components.
- Example: Bacteriophages.
- Function: Tail fibres in bacteriophages, for instance, aid in attaching to specific bacterial cells.
Viral Envelopes
- The presence or absence of an outer envelope further distinguishes viruses.
Enveloped Viruses
- Possess an outer lipid bilayer membrane, typically derived from the host cell's own membrane during viral replication or budding.
- Function: The envelope may contain viral proteins or glycoproteins essential for binding to host cells, facilitating viral entry.
- Examples: HIV, Influenza viruses.
- Vulnerability: They are more susceptible to environmental factors and detergents.
Non-enveloped Viruses
- Lacking the lipid bilayer, they're more robust structurally.
- Function: They rely on their capsid alone for protection and interaction with host cells.
- Examples: Norovirus, responsible for stomach flu; Rhinovirus, causing common cold.
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Description
This quiz covers the genetic material in viruses, including DNA viruses with double-stranded DNA and their examples. Learn about the genetic blueprint of viruses and how they function.
